Sickle Guard Shape for Use in a Sickle Cutter System with Increased Ground Speed

ABSTRACT

In a sickle cutting system, it has been found that a significant increase in ground speed while maintaining an acceptable level of cutting efficiency as measured by the average stubble length can be obtained by a combination of one or more of the features where the cutting stroke is reduced from the conventional length of 3.0 inches to a value of the order of 2.0 inches; the length of the cutting edge of each knife blade is increased to a length greater than 2.2 inches; the width at the rear of the ledger surface of each guard is increased to greater than 1.0 inches; and the front edge of the blade is formed with an apex to shed crop material to one or other side of the apex.

This application claims the benefit under 35 USC 119(e) of ProvisionalApplications U.S. 61/587,843 filed Jan. 18, 2012; U.S. 61/664,345 filedJun. 26, 2012; 61/677,169 filed Jul. 30, 2012 and U.S. 61/677,177 filedJul. 30, 2012.

This invention relates generally to a sickle guard for a sickle knifecutter system for harvesting crop with improved cutting action which mayallow increased ground speed while maintaining cutting efficiency and/orstubble height at an acceptable level.

BACKGROUND OF THE INVENTION

The present invention relates generally to a crop cutting devicecomprising a frame structure arranged for forward travel over groundhaving a standing crop thereon; a cutter bar secured to the framestructure and extending transversely across a front end of said framestructure; a plurality of knife guards mounted in spaced relation alongsaid cutter bar and projecting forwardly therefrom in transversealignment; each of said guards having an upwardly facing ledger surfacewith opposed side edges thereof arranged to provide first and secondshearing edges; a sickle bar mounted in transversely extending positionand being driven for reciprocating movement relative to said knifeguards; the sickle bar having a plurality of knife blades mountedthereon for movement therewith; each of the knife blades having acutting surface for passing across the ledger surface of the knifeguards and an opposed surface; each of the knife blades having two sidecutting edges which are beveled from the opposed surface to the cuttingsurface to cooperate with said shearing edges of said knife guards; thesickle bar being driven to carry the knife blades back and forth betweenthe knife guards.

It is well known that many sickle knives of this general type include aconventional or pointed guard where the guard is formed as an integralelement which includes a base piece attached to the cutter bar anddefining the ledger surface and a nose piece projecting forwardly fromthe ledger surface in front of the front edge of the blade which isgenerally pointed at a leading end so as to separate the crop to eachside of the guard. This nose piece also stands up in front of the ledgersurface to protect the front edge of the blade and includes a rearwardlyextending shelf over the ledger surface which forms a slot with theledger surface through which the blade passes. Guards of this typeinclude separate hold down members between the guards which applydownward pressure on the cutter bar to press the blades against theledger surface.

Pointed guards generally feature a point with a cut slot that the sickleblades reciprocate in and out of. Various types of hold-down arrangementare used to apply pressure to the sickle to keep its shearing surface inclose contact with the guard ledger as cutting occurs. Usually these arelocated between the guard point or at the rear edge of the sickles. Mostare sheet metal and feature easy adjustment using a hammer or a simplesingle point threaded adjustment. By keeping the hold-downs separatefrom the guards fewer hold-downs than points may be used to reduce thecost and number of adjustments required. Pointed guards have found muchfavor in easier cutting conditions due to the ease of adjustment andsuperior performance.

Another form of guard is known as a stub guard which is formed in twoseparate pieces including a base piece which carries the ledger surfaceand a top piece which extends over the ledger surface. The pieces areseparate and separately adjustable relative to the cutter bar so thatthe top piece can apply pressure onto the blade to press it onto theledger surface. The pieces terminate at a front edge which is justbehind the front edge of the blade so that the front edge of the bladeis presented to the crop.

In tough cutting, stub or no-clog guards have found the most favor. Stubguards use a separate top and bottom guard pieces that spaced slightlymore than one sickle blade thickness apart create a slot for the bladeto operate in. The front edge of the blade protrudes slightly past thefront tip of the two guards. This feature is what originally gavestub-guards their non-clogging self-cleaning action. A major improvementin stub guard technology was made when fully adjustable top hold-downassemblies were introduced. These arrangements allowed the gap to becontrolled much more precisely than previously so that the shearingsurface of the blade was kept in close contact with the guard ledgersurface. This adjustability allows the stub top piece to act as a muchmore effective hold-down than the hold-downs found on regular pointedguard systems.

The pointed guard has an advantage of presenting a point to the incomingcrop so that crop is effectively divided around it. This is especiallyadvantageous when the sickle blade is at or near the end or start ofeach stroke and a front edge of each blade, which is typically a bluntfront edge of a width of the order of 0.5 inch, is hidden partially orentirely within the guard slot. Since the sickle bar velocity is lowestat or near the end or start of each stroke this gives the pointed guarda considerable advantage over the stub guard for most crops.

The guards can be formed as single elements separately mounted on theguard bar or as double or triple elements connected together side byside for common mounting and common adjustment relative to the guardbar. There is no reason why more elements might be included but this isnot typical.

In some cases the arrangement is of the double sickle type where eachsickle bar is essentially half the length of the cutter bar and thecutter bars reciprocate in opposite phase to minimize vibrating mass andvibrations. Usually the sickle bars are timed so that they move inopposite directions so that vibrations induced into the cutter barassembly are minimized.

The sickle knife cutting system has been widely accepted as the mostpower efficient system due to the shearing action. However due to speedrestrictions of generally less than 5 to 8 mph ground speed, othersystems such as rotating flail systems have come into use since thesecan be operated at much higher ground speed of up to 14 mph whilemaintaining a high cutting efficiency. Such rotary systems have howevermuch higher power usage, are limited in width and provide crop handlingdifficulties for forming effective swaths for drying of the crop.

It remains therefore an ongoing and highly desirable objective toconstruct a sickle knife system which can cut standing crop withsufficient cutting efficiency that the ground speed can be significantlyincreased. It is believed that the construction of a sickle cuttingsystem which can operate at ground speeds of greater than 5 to 8 mph andup to 14 mph would enable the advantages of the sickle cutting action totake back the market currently being met by the flail systems.

Cutting crops such as soy beans where the bean pods can be locatedclosely adjacent the ground typically requires low ground speeds ofaround 4 to 5 mph to ensure that the crop is cut and fed into thecombine harvester without too much loss of the pods. Pods can be lost ifthe cutting action causes some or too many of the lowest pods to be leftat the stubble or broken up by the cutting action. It would be highlydesirable to increase cutting speed above the typical range of 4 to 5mph so as to increase this to or above 6 mph.

Cutting crops such as hay or forage crops such as alfalfa or grassestypically allows higher ground speeds of up to 10 mph since the crop ismore resistant to a poor or inefficient cutting action. It would behighly desirable to increase cutting speed above the typical range of upto 10 mph so as to increase this to or above 12 or even 14 mph.

The term “sickle bar” as used herein is intended to refer generally to astructure which supports all of the knife blades at the spaced positionsalong its length and is not intended to be limited to a singlecontinuous element extending along the whole length of the structure.Thus the bar may be formed of different elements at different parts ofthe length and may include pieces below and above the blades.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide a guard for asickle cutting apparatus which can provide an improvement in cuttingefficiency leading to a possible increase in ground speed.

According to the invention there is provided a knife guard for use in asickle cutting apparatus comprising: a frame structure arranged forforward travel over ground having a standing crop thereon; a cutter barsecured to the frame structure and extending transversely across a frontend of said frame structure for receiving a plurality of stationaryknife guards mounted along the cutter bar and projecting forwardlytherefrom; a sickle bar mounted in transversely extending position andbeing driven for reciprocating movement relative to said guard fingers;the sickle bar having a plurality of knife blades mounted thereon formovement therewith; each of the knife blades having a cutting surfacefor passing across the knife guards; each of the knife blades having onfirst and second sides first and second side cutting edges to cooperatewith shearing edges of said guard guards; comprising:

a base portion for mounting on the cutter bar;

at least one guard finger mounted on the base portion so that thefingers are arranged in a row along the cutter bar with a space betweeneach finger and the next allowing crop to enter the space;

the guard finger having an upwardly facing ledger surface with opposedside edges thereof arranged to provide first and second shearing edges;

a center line spacing between each guard finger and the next being lessthan 3.0 inches;

wherein a width of each guard at a rearmost cutting portion of ledgersurface is greater than 1.5 inches.

GENERAL DESCRIPTION

It has been found, as described hereinafter, in relation to theembodiments particularly described, that a significant increase inground speed while maintaining an acceptable level of cutting efficiencyas measured by the average stubble length can be obtained by acombination of one or more of the features where:

a) The distance between the center line of the guards which is generallyequal to the distance between the center line of the blades is reducedfrom the conventional length of 3.0 inches. This distance may be equalto the stroke length so that a shorter stroke length can allow asignificant increase in reciprocation rate. However the stroke lengthmay be a multiple of the center line distance. Even where the stokelength is not reduced so that the increase in reciprocation rate cannotbe achieved, the reduced center line distance has been shown to providea significant advantage.

b) the length of the cutting edge of each knife blade as measured from arearmost end of a cutting action to a forwardmost tip of the knife bladeis increased from a conventional length to a length greater than 2.2inches.

c) the width of the ledger surface of each guard at a position thereonaligned with the rear end of the cutting edge of each knife blade isincreased from a conventional length to a length greater than 1.0inches.

d) the front edge of the blade is formed with a pointed portion wherethe shape of an apex and side edges of the pointed portion are arrangedto shed crop material engaging the point portion as the point portion ismoved forwardly in the crop to one or other side of the point portionfor cutting and to avoid pushing crop forwardly by the point portion.

This combination surprisingly provides a crop cutting efficiency whichis sufficiently high that the ground speed can be increased from theconventional of the order of 5 to 8 mph to 12 to 14 mph. This increaseis significant and significantly alters the ability of the draper headerto harvest forage crops such as alfalfa at greater than 10 mph and up to14 mph and to harvest soy beans at greater than 5 mph and up to 6 or 7mph.

The invention herein can be defined as or relate to the method ofcutting, the header for cutting, the guards and/or the knife blades.Thus each of these components of the invention includes aspects of theinvention which distinguish that component from the prior art as definedhereinafter.

Blade Length

A first improvement can therefore be obtained by providing a knife bladewhich is narrower than conventional system so that typically the widthis equal to approximately 2.0 inches center to center while providing ablade which has a length greater than conventional system so that thelength from the trash bar to the tip is greater than 2.0 inches andtypically of the order of or greater than 2.75 inches.

This can be further combined with an arrangement in which the width ofthe guard at the trash bar is increased so that the width of each guardat the rear trash bar is equal to the maximum width which can beobtained while leaving a space at the trash bar between the ledgersurfaces of the order of 0.5 inch or the distance necessary to avoidpinching of crop stalks between the ledger surfaces.

Typically each of the knife blades is generally triangular in shape sothat the side edges converge to a front edge at an angle of the order of60 degrees to the direction of reciprocating movement. The blade has abottom cutting surface for passing across the ledger surface of theknife guards and an opposed or upper surface. The two converging sidecutting edges are beveled from the upper surface to the bottom cuttingsurface to cooperate with the shearing edges of said knife guards. Inaddition the beveled side edges are typically serrated with groovesrunning in a direction longitudinal to the reciprocating direction. Inorder to maximize the cutting action, the length of the cutting edge issubstantially the maximum length extending from the trash bar at therear to a position close to the front edge of the blade.

The fore-aft length of a blade has traditionally been in the order of 45mm (1.75 in) from the front of the trash bar, that is the rearmostcutting location or the rear of the cutting action, to the tip of thesection, or 55 mm (2.2 in) from the front edge of the knife back to thetip of the section. Traditionally this dimension is usually similar tothe length of the cutting edge.

In this new arrangement, the fore-aft length of the blade is increasedsubstantially. Thus the length of cutting edge of each sickle blade froma rearmost end of the cutting action at the trash bar, or to the rear ofthe shearing action on the ledger surfaces, to a front edge of the bladein the present invention is greater than 1.75 inches. This can lie inthe range 2.2 to 3.0 inches.

The term “trash bar” as used herein does not require the provision of aspecific bar member extending across the blades but merely relates tothe position of that component of the system where the crop is halted asit moves rearwardly between the guard fingers. Thus at some point thecrop is halted so that it remains in the position where it can beengaged by the side edges of the blades and can be cut in the shearingaction relative to the side edges of the ledger surface. This elementwhich halts the crop movement is called herein the “trash bar”.

This also reduces the angle of inward inclination of the cutting edgefrom the typical 30 degrees to an angle less than 20 degrees andtypically of the order of 15 degrees and in the range 15 to 30 degrees.

Thus in one example the blade has a width of 2.0 inches at the base anda length from the front of the trash bar to the tip of 2.5 inches.

Pointed Blade Tip

It is common practice for sickle sections, of the current type havingbeveled and serrated side edges, to have a front edge in the order of 15mm (0.6 inches) wide. When used with a pointed guard, this is not asmuch of a problem as this edge is sometimes in the shadow of the guard.However, even with pointed guards and certainly when used with stubguards, the wide tip has the potential for running down crop or pushingthe crop forwardly with the forward motion of the cutter bar, thusleaving more long uncut stems greater in length than the nominal minimumvalue above thus significantly increasing the average length with is themeasure herein of cutting efficiency. In present invention the blade isdesigned with a pointed tip, thus eliminating the problem when used withstub guards.

In some crop conditions e.g. forage with a mat of wet leaves near theground, pointed guards will tend to plug due to “mouse nesting” on theguard point. It is therefore important that a cutting system works wellwith stub guards. The intention is therefore to provide a sickle bladewhich is as pointed as reasonably practical. A sharp point is difficultto obtain so that typically the front edge is smoothly curved with aradius of curvature less than 0.5 inches thus defining a front apexwhich is sufficiently narrow to shed crop stalks to each side. That is,each knife blade has a front point portion in front of the cutting edgeswhich has side edges converging to front apex where the apex and theside edges are shaped and arranged such that crop material engaging thepoint portion, as the point portion is moved forwardly in the crop, isshed to one or other side of the point portion for cutting and is notpushed forwardly by the point portion. In the present arrangement thefront apex is not a point as this can be damaged but is a curved frontedge of a radius of curvature less than 0.5 inches and preferably lessthan 0.25 inches. From this curvature the sides of the pointed portiondiverge rearwardly at an angle approximately equal to or slightlygreater than the angle of the cutting edges.

In a blade which has a center to center spacing of the order of 2.0inches and a length from apex to trash bar greater than 2.0 inches, theangle of the side edges of the blade is less than 20 degrees and can beas low as 15 degrees.

The angle of the side edges of the front point portion can be greaterand is typically in the range 30 to 45 degrees and preferably of theorder of 35 degrees.

This curvature at the apex and the angle of divergence from the curvedapex acts to shed the crop to the sides and to avoid trapping andpushing the crop forwardly.

While this is the optimum arrangement, a practical construction may havea straight line across the apex with a transverse width which is muchless than the conventional 0.6 inches and is typically less than 0.25inches.

Thus each knife blade has a front point portion in front of the beveledand serrated side cutting edges which front point portion has side edgesconverging to front apex, where the apex and the side edges of the frontpoint portion are shaped and arranged such that crop material engagingthe front point portion, as the point portion is moved forwardly in thecrop, is shed to one or other side of the front point portion forcutting by the side cutting edges and is not pushed forwardly by thefront point portion.

Preferably the beveled side sedges are serrated in a direction at rightangles to a forward direction.

Preferably the pointed portion has a thickness at the apex equal to thatof the blade.

Preferably the beveled edges are reduced in width at as they approachthe pointed portion leaving a strip of the upper surface between thebeveled edges having thickness equal to that of the blade with sideedges of the strip being parallel to the center line of the blade.

Preferably at this strip the beveled edges become narrower as thebeveled edge approaches the front pointed portion of the blade.

Preferably the beveled edges and the serrations therein terminate at aposition spaced from the apex of the pointed portion such that the frontpointed portion forms an arrow-head shape in front of a forwardmost oneof the serrations with the width of the front pointed portion beingsubstantially equal to the width of the side edges at the forwardmostone of the serrations.

Preferably a center line spacing between each knife blade and the nextis less than 3.0 inches, preferably less than 2.5 inches and morepreferably of the order of or equal to 2.0 inches.

Preferably a length of each knife blade from the trash bar to aforwardmost tip of the knife blade is greater than 2.0 inches,preferably greater than 2.5 inches and more preferably greater than 2.75inches.

Preferably the front point portion has side edges which are notsharpened.

Preferably the radius of curvature of the front pointed portion at theapex is less than 0.5 inch and more preferably less than 0.25 inch.

Blade Shape

The characteristics of the blade defined above where it is much narrowerthan conventional, 2.0 inches as opposed to 3.0 inches, andsignificantly longer, 2.5 to 2.75 inches as opposed to 2.2 inches placesconsiderable limitations on the shape and arrangement of the beveled andserrated edges.

In order to form the pointed portion at the front edge in front of thebeveled edges, the beveled edges are reduced in width as they approachthe front edge leaving a strip of the upper surface between the bevelededges with side edges of the strip parallel to a center line of theblade. Thus at this strip the beveled edge becomes narrower and thegrooves in the edge get shorter as the beveled edge approaches the frontapex of the blade. The beveled edges and the serrations thereinterminate at a position spaced from the front apex to define anarrow-head shaped pointed portion in front of the beveled edges whichimparts sufficient strength to the construction to allow the formationof the serrations. The thickness of the blade through the main body ofthe blade excluding the beveled edges is constant so that the pointedportion and the apex have the same thickness as the rest of the mainbody of the blade and the bevel which reduces the thickness does notextend to the apex.

Width of Guard Cutting Edge

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge of the knife guard. Generally, the widthat the rear of the cutting edge on the guard is in the order of 25 mm(1.0 in). In the arrangement of the present invention that width issubstantially increased. Thus the width of each guard at a positionthereon aligned with the rear end of the cutting edge of each blade isgreater than 1.0 inches. The maximum width of the guard is slightly lessthan the center to center spacing of the blades since it is necessary toleave a gap between the guards at the back to prevent pinching the cropand to allow the crop to reach the back for the rearmost cutting action.Thus with a blade center to center spacing of 2.0 inches the width ofthe guard is slightly less than that of the width of the blade orroughly 1.9 inches. Thus with a blade of this width, the width of theguards can be as much as 1.9 inches and preferably lies in the range 1.2to 1.9 inches. However where the blade is greater than 2.0 inches inwidth, the guard has a width which is between 0.5 and 0.1 inches lessthan the width of the blade.

Thus the arrangement provided herein provides a center line spacingbetween each guard finger and the next which is less than 3.0 inches andmore preferably 2.0 inch where a width of each guard at the rear trashbar is greater than 1.5 inches and preferably 1.75 inches.

Thus a width of each guard at the rear trash bar is equal to the maximumwidth which can be obtained while leaving a space at the trash barbetween the ledger surfaces of the order of 0.5 inch or the distancenecessary to avoid pinching of crop stalks between the ledger surfaces.

Preferably the stroke length is equal to the center line spacing betweenthe knife blades.

Preferably, at the position in the stroke where the center line of theknife blades is aligned with the center line of the guard fingers, theside cutting edges of the knife blades substantially directly overliethe side edges of the ledger surface.

Preferably each knife blade has a front point portion in front of theside cutting edges which front point portion has side edges convergingto front apex, where the apex and the side edges of the front pointportion are shaped and arranged such that crop material engaging thefront point portion, as the point portion is moved forwardly in thecrop, is shed to one or other side of the front point portion forcutting by the side cutting edges and is not pushed forwardly by thefront point portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a part of header showing a portion of thesickle knife according to a first embodiment of the present inventionusing a stub guard.

FIG. 2 is a cross-sectional view along the lines 2-2 of FIG. 1.

FIG. 3 is top plan view of a knife blade for use in the sickle knife ofFIG. 1.

FIG. 4 is a side elevational view along of the knife blade of FIG. 3.

FIG. 5 is top plan view of one knife blade of FIG. 3 on an enlargedscale showing the angles of the side edges for different length blades.

FIG. 6 is top plan view of a knife blade of the type of FIG. 3 showing adifferent width blade.

FIG. 7 is a top plan view of a part of header showing a blade of asickle knife according to a second embodiment of the present inventionusing a pointed guard.

FIG. 8 is a cross-sectional view along the lines 8-8 of FIG. 7.

DETAILED DESCRIPTION

In FIGS. 1 and 2 is shown a first embodiment of a crop cutting devicegenerally indicated at 10. Only a part of the complete machine is shownsince the remainder of the machine may vary widely depending uponrequirements and since the construction is of course well known to aperson skilled in the art. In this embodiment as shown, there is a framegenerally indicated at 11 which forms only one part of the total framestructure that is the part of the frame that is relevant to the presentinvention.

The cutting device 10 further includes a cutter bar 12 attached to theframe structure 11. Thus the frame structure 11 in the part as showncomprises a guard bar 13 to which is attached a plurality of knifeguards 14. The guard bar 13 is attached to the frame structure whichsupports the guard bar in fixed position across the front edge of theframe for a cutting action of the crop cutting device on the standingcrop.

Each knife guard 14 includes one or more guard fingers 14A so thatguards can be arranged with a single finger, pair of fingers or triples.As shown the guard bar forms a triple guard construction with threefingers where a series of such guards are mounted on the guard bar 13 atspaced positions along the length of the guard bar. In the embodiment asshown, only one of the guards is shown but it will be appreciated thatthere are additional guards as required to provide a crop cutting deviceof a required width.

The knife guards shown in FIGS. 1 and 2 are basically of a conventionalconstruction of a stub guard in that each guard finger 14A includes alower portion 15 and an upper portion 16. These two portions are mountedon the guard bar 13 by a mounting arrangement 17 including bolts 18. Themounting arrangement thus attaches a rear end 19 of the lower portion 15rigidly on the underside of the bar 13 so that the fingers of the guardproject forwardly from the bar to a front nose 20. Similarly the upperportion 16 is mounted on the guard bar 13 by an adjustment plate 21attached onto the same bolts 18. Upper portion 16 has fingers whichextend forwardly to a nose 22.

In the embodiment shown the guards are stub guards so that the noses 20,22 of the upper and lower portions substantially overlie one another andconfine between them the blades 23 of the sickle bar or knife back 24.

Each pair of guards thus includes two guard elements each defined by anupper portion and a lower portion and the guard elements are shown inFIG. 1 at 15 and 16. A front crop guide bar or trash bar 28 is alsoprovided. Between the mounting bar 21 and the front guide bar 28 isprovided a channel 25 within which the sickle bar or knife back 24 ismounted for reciprocating movement.

The trash bar may form a continuous bar member extending along the lowerguard portion 15 in front of the bar 24 to prevent any crop reachingthat area. However the trash bar may be formed by any part of the systemwhich prevents the crop from moving rearwardly beyond the rear end ofthe cutting edges of the blades. There may be a single sickle bar drivenfrom one end or in some cases there are two sickle bars driven fromopposite ends and meeting in the middle. The sickle bar or bars aredriven by the reciprocating drive motor (not shown but conventional)such that the bar reciprocates back and forth.

In some cases the bar reciprocates by a distance S1 equal to the spacebetween the nose of one guards 15, 16 and that of the next along theguard bar 13 so that the blades reciprocate from a position with thecenter line of the knife aligned with the center line of the first guardto a position aligned with the next and back to the first. In othercases, the reciprocation stroke may be as shown at S2 a multiple of,typically double, the distance between the guards so that the knifemoves from a first guard finger across a second to a third and back tothe first. This arrangement reduces the available reciprocation rate dueto increased acceleration forces but reduces the number of reversals.

The following table shows the set stroke rate in rpm to be used in thecalculation of inefficiency for different speeds and stroke length.

6 MPH 10 MPH 14 MPH Typical RPM Typical RPM Typical RPM 2″ stroke 735918 1102 3″ stroke 600 750 900 4″ stroke 520 650 779

Each sickle bar comprises the support bar member 24 and the plurality ofblades indicated at 23. As shown the blades are formed in pairs mountedon a common base as shown in FIG. 3, but individual blades may beprovided or in some cases the blades may have more than two on the samebase.

Each of the blades forms a generally triangular-shaped member which hasa rear end or base 23A bolted to the bar and converges from the rear endto a front end 23B. Each of the blades has a top surface 23D and abottom surface 23E.

Each of the blades has a side edge 23F and a second side edge 23G. Thesides edges are beveled from the top surface down to the bottom surface23E so that a sharp edge is formed at the bottom surface at each of theside edges. The blades are also serrated at each cutting edge withgrooves 23L, 23M extending parallel to the bars 24 that is at rightangles to a center line 23H.

The top member 16 acts to hold the blades downwardly into engagementwith the top ledger surface 15A of the bottom portion 15. The bottomportion 15 has two side edges of the ledger surface 15A as best shown inFIG. 2 with those side edges 15B and 15C acting as side edges of theledger surface 15A. Thus the cutting action of the blades occurs betweenthe ledger 15A and the bottom surface 23E of the blade as the bladereciprocates from its position at one of the guards to its position atthe next adjacent one of the guards. In this cutting action, therefore,the side edge of the blade moves across the space between the guards andenters onto the ledger surface of the next guard in a cutting actionbetween the bottom surface of the blade and the top surface of the guardwhich are immediately adjacent and generally in contact or at leastclosely adjacent to provide a shearing action on the crop.

In these guards, the upper portion 16 acts merely as a hold down membercontacting the upper surface of each of the blades so as to prevent itfrom moving away from the ledger surface 15A by applying pressure tothat upper surface 23D of the blade and holding the blade in contactwith or closely adjacent the ledger surface 15A of the bottom portionwhere the cutting action occurs. The upper portion 16 therefore as shownin FIG. 1 has side surfaces 16B and 16C of the bottom surface 16A whichis narrower than the ledger surface 15A of the bottom portion 15.

The mounting and adjustment arrangements for the bottom portion 15 andthe upper portion 16 can vary in accordance with a number of differentdesigns readily available to a person skilled in the art. It suffice tosay that the hold down portion 16 is adjustable so that the gap betweenthe bottom surface of the hold down portion and the ledger surface ofthe bottom portion 15 can be adjusted to allow the sliding action of theblades while holding the blades in the required position.

The disclosures of the following documents of the present Applicants areincorporated herein by reference or may be referred to for details ofthe construction not provided herein. These show various conventionaldetails of the sickle knife system which can be used in the arrangementherein but are not described as they are known to persons skilled in theart.

U.S. Pat. No. 7,328,565 (Snider) issued Feb. 12, 2008;

U.S. Pat. No. 4,894,979 (Lohrentz) issued Jan. 23, 1990

U.S. Pat. No. 4,909,026 (Molzahn) issued Mar. 20, 1990.

U.S. Pat. No. 6,962,040 (Talbot) issued Nov. 8, 2005.

U.S. application Ser. No. 13/680,557 filed Nov. 19, 2012 based on aProvisional application 61/577,427 filed Dec. 19, 2011 (Talbot) relatingto an adjustable hold down.

In FIG. 1, a drive for knife bar 24 is indicated schematically at 24A.This can comprise any suitable drive system known to persons skilled inthis art of a type which can generate a stroke S1 of 2 inches at a driverate of typically 918 rpm. The system can also be arranged in analternative embodiment to drive the stroke S2 of 4 inches in which casethe reciprocation rate may be lower. The drive system 24A includes aninput from a ground speed indicator 24B which allows automatic adjustingof the stroke rate of the drive system 24A in dependence on groundspeed. As the system herein provides a cutting efficiency which ishigher than that of previous designs and suitable for cutting at speedsas much as 14 mph, it is possible when running at lower ground speedssuch as less than 10 mph to reduce the drive rate of the knife since themaximum cutting effect is not required at those lower ground speeds.Thus the system can be arranged to automatically control the knife speedto a lower fixed value when the ground speed is less than apredetermined set value or to provide a proportional control of thedrive speed.

The knife blade 23 is narrower than conventional system so thattypically the width W is equal to the stroke length which isapproximately 2.0 inches center C to center C while providing a bladewhich has a length L greater than conventional system so that the lengthfrom the trash bar 28 to the tip 23K is greater than 2.0 inches andtypically of the order of or greater than 2.75 inches.

This can be further combined with an arrangement in which the width W1of the guard ledger surface at the trash bar 28 is increased so that thewidth W1 of each guard at the rear trash bar is equal to the maximumwidth which can be obtained while leaving a space S at the trash barbetween the ledger surfaces of the order of 0.5 inch or the distancenecessary to avoid pinching of crop stalks between the ledger surfaces.

Typically each of the knife blades is generally triangular in shape withstraight side edges 23F, 23G. However other shapes of the side edges23F, 23G in plan such as convex or concave can be used. Thus the sideedges 23F, 23G converge to the front apex 23K at an angle of the orderof 60 degrees to the direction of reciprocating movement. The twoconverging side cutting edges 23F, 23G are beveled from the uppersurface 23D to the bottom cutting surface 23E to cooperate with theshearing edges of the knife guards. In addition the beveled side edgesare serrated with grooves 23L, 23M running in a direction longitudinalto the reciprocating direction. In order to maximize the cutting action,the length of the cutting edge is substantially the maximum lengthextending from the trash bar 28 at the rear to a position close to thefront apex 23K of the blade.

In this new arrangement, the conventional fore-aft length of the bladeis increased substantially. Thus the length of cutting edge of eachsickle blade from a rearmost end of the cutting action at the trash bar28, or to the rear of the shearing action on the ledger surfaces 15A, tothe front apex 23K of the blade in the present invention is greater than1.75 inches. This can lie in the range 2.2 to 3.0 inches.

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge of the knife guard. In the arrangement ofthe present invention that width is substantially increased. Thus thewidth W1 of each guard at the trash bar 28 is greater than 1.0 inches.The maximum width of the guard is slightly less than the center tocenter spacing of the blades since it is necessary to leave the gap Sbetween the guards at the back to prevent pinching the crop and to allowthe crop to reach the back for the rearmost cutting action. Thus with ablade center to center spacing of 2.0 inches the width W1 of the guardis slightly less than that of the width of the blade or roughly 1.9inches. Thus with a blade of this width, the width of the guards can beas much as 1.9 inches and preferably lies in the range 1.2 to 1.9inches. However where the blade is greater than 2.0 inches in width, theguard has a width which is between 0.5 and 0.1 inches less than thewidth of the blade.

At the position in the stroke shown in FIG. 1 where the center line C ofthe knife blades is aligned with the center line C1 of the guardfingers, the side cutting edges of the knife blades 23F, 23Gsubstantially directly overlie the side edges 15B, 15C of the ledgersurface 15A.

Each knife blade has a front point portion 23X in front of the sidecutting edges 23F, 23G which front point portion has side edges 23N, 23Pconverging to the front apex 23K, where the apex and the side edges ofthe front point portion 23X are shaped and arranged such that cropmaterial engaging the front point portion, as the point portion is movedforwardly in the crop, is shed to one or other side of the front pointportion for cutting by the side cutting edges and is not pushedforwardly by the front point portion 23X.

As shown in FIGS. 3, 4 and 5, the arrow head shaped front point portion23X has side edges 23N, 23P which are not sharpened. The angle of thebevel of the sides 23F and 23G may extend partly into the side edges 23Nand 23P but the side edges 23N and 23P are not beveled to the bottomsurface 23E so that they are not sharp. Also the last serration 23Y ofthe bevel edges 23F and 23G is located at the bottom of the portion 23Xso that the side edges 23N and 23P are not serrated. The pointed portion23X has a thickness at the apex 23K equal to that of the blade so thatas shown in FIG. 4B, the thickness along the center line remainsconstant right up to the apex 23K. The arrangement is designed so thatthe front portion 23X is as thick as possible over its full extentconsistent with the requirement to machine the blade to form the beveledand serrated edges 23F, 23G. Thus the beveled side edges 23N and 23P arereduced in width in plan view at as they approach the pointed portion23X leaving a strip 23R of the upper surface between the beveled edgeshaving thickness equal to that of the blade with side edges 23Q of thestrip being parallel to the center line 23H of the blade. Thus, at thisstrip 23R, the beveled side edges 23N and 23P become narrower as thebeveled side edges 23N and 23P approach the front pointed portion 23X ofthe blade.

The beveled side edges 23N and 23P and the serrations 23L thereinterminate at the position 23Y spaced from the apex 23K of the pointedportion 23X such that the front pointed portion 23X forms an arrow-headshape in front of a forwardmost one 23Y of the serrations with the widthof the front pointed portion 23X being substantially equal to the widthof the side edges 23N and 23P at the forwardmost one 23Y of theserrations.

As shown in FIGS. 3 and 4, a center line spacing CLS between each knifeblade and the next is less than the conventional value of 3.0 inches andpreferably of the order of or equal to 2.0 inches. It will beappreciated that a measurement of center to center spacing which isequal to an integral number of inches is preferred for engineeringreasons but in theory it is not essential to have an integral number andin some cases the spacing can be in millimeters. In practice, a spacingin the range 2.5 to 1.5 inches is suitable. In FIG. 6 (not to scale) awider spacing of 2.5 inches is shown. In FIG. 5 the angles of differentlengths of blade are shown where a blade having a length of at least 2.5inches from the trash bar is shown having an angle A2 of the side edgesand a shorter blade having a length of the order of 2.0 inches from therash bar has angles A3. In each case the angles of the side edges 23Nand 23P is slightly greater than that of the cutting edges.

As shown in FIGS. 3 and 4, a length L along the center line 23H of eachknife blade from the trash bar that is the rearmost end 23T of thecutting edge 23F to the forwardmost tip 23K of the knife blade issubstantially equal to or greater than 2.75 inches. Improvement incutting efficiency is obtained by increasing the length of the blade sothat the selection of a value of at least 2.75 inches is preferred whichprovides the improved cutting action while avoiding a blade which has alength greater than can be manufactured to remain stiff and straight inthe cutting action without danger of bending. Improvement can beobtained at any value greater than conventional blades so that any valuegreater than 2.0 inches is within the invention herein. A length greaterthan 2.5 inches will provide a significant improvement.

In order to provide shedding of crop at the apex, the radius ofcurvature of the front pointed portion at the apex is less than 0.5 inchand preferably less than 0.25 inches. However a blunt front edge ispossible provided it is sufficiently narrow and a value of less than0.25 inch or more preferably less than 0.125 inch is possible.

The above geometry provides a construction in which the side edges ofthe blade are arranged relative to a center line of the blade at anangle less than 30 degrees and preferably less than 25 degrees.

Similarly the side edges of the front portion, which are typically butnot necessarily at the same angle as the side edges of the blade, arearranged relative to a center line of the blade at an angle less than 30degrees and preferably less than 25 degrees. In practice this angle ispreferably of the order of 20 degrees.

Thus the preferred construction provides a center line spacing betweeneach knife blade and the next is of the order of or equal to 2.0 inches,the radius of curvature of the front pointed portion at the apex is lessthan 0.25 inch and the side edges of the front portion are arrangedrelative to a center line of the blade at an angle of the order of 20degrees.

As shown in FIG. 1, the width between the centers of the guards isindicated at D. This can be the same as the length of the cutting strokeso that the blades move from a position aligned with the center line ofone guard finger to that of the next. However in some embodiments thestroke may be a multiple of the distance D, typically twice, so that theblades move from the first guard finger to the third crossing thesecond. The reversal of the reciprocating action at the guard centerline ensure that the blades are stationary and therefore carrying out nocutting when they are overlying the guard and not at an intermediatelocation. The increase of the stroke length to a multiple of the fingerreduces the number of times the blades are stationary but requires areduced stroke rate due to the increased forces on the drives system.

This distance D is less than 3.0 inches and is more preferably of theorder of 2.0 inches. Typically the stroke can lie in the range 1.5 to2.5 inches since this provides a stroke length which allows an increasein the cutting reciprocation rate of the sickle bar by a percentage ofthe order of 22%. This allows a typical rate of 600 cycles per minute,suitable for a 40 ft sickle bar, to be increased a rate greater than750. For shorter bars this rate can be greater than 900. The length ofthe stroke and the rate are determined by the selected geometry of thedrive system. Typically each of the knife blades 23, as shown in FIG. 2,is generally triangular in shape. In the example shown, the blade 23forms a double blade connected by a base 23A. The base has holes 23J formounting on the blade drive bar 24. The blade 23 has two side edges 23F,23G which converge at an angle A to the direction of reciprocatingmovement. At the front of the blade is provided a front apex 23K of afront arrow head shaped portion 23X.

The blade has a bottom cutting surface 23E for passing across the ledgersurface 15A of the bottom knife guards 15 and an opposed or uppersurface 23D. The two converging side cutting edges 23F, 23G are beveledfrom the upper surface 23D to the bottom cutting surface 23E tocooperate with the shearing edges of the knife guards. In addition thebeveled side edges 23F, 23G are typically serrated with grooves 23L, 23Mrunning in a direction longitudinal to the reciprocating direction. Inorder to maximize the cutting action, the length of the cutting edge issubstantially the maximum length extending from the trash bar 28 or therear edge 23T at the rear to a position at the front edge or tip 23K ofthe blade.

The fore-aft length of a blade has traditionally been in the order of1.75 inches from the front of the trash bar to the tip of the section,or 2.2 inches from the front edge of the knife back to the tip of thesection.

In this new arrangement, the fore-aft length L of the blade is increasedsubstantially. Thus the length of the cutting edges of each sickle bladeor blade is greater than 2.2 inches. This can be as much as 2.6 inchesand can lie in the range 2.2 to 3.0 inches.

This also reduces the angle A of inward inclination of the cutting edgefrom the typical 30 degrees relative to the center line (an equilateraltriangle) to an angle less than 30 degrees and typically of the order of15 degrees and in the range 15 to 30 degrees.

It is common practice for sickle blades to have the front edge as atransverse straight edge in the order of 0.6 inches wide. The wide tiphas the potential for running down crop, thus leaving long uncut stems.In the present invention the blade is designed with a pointed tip orfront apex 23K, thus eliminating the problem.

The intention is therefore to provide a sickle blade which is as pointedat the front apex 23K as reasonably practical. A sharp point isdifficult to obtain so that typically the front apex 23K is smoothlycurved with a radius of curvature R of a curvature circle C less than0.5 inches thus defining the front apex 23K which is sufficiently narrowto shed crop stalks to each side.

Each knife blade therefore has a front point portion in front of thecutting edges which has side edges 23N, 23P converging to front apexwhere the apex and the side edges are shaped and arranged such that cropmaterial engaging the point portion as the point portion is movedforwardly in the crop is shed to one or other side of the point portionfor cutting and is not pushed forwardly by the point portion.

While this is the optimum arrangement, a practical construction may havea transverse width of a straight line across the apex 23K which is muchless than the conventional 0.7 inches and is typically less than 0.25inches. This narrow front edge is selected to be sufficiently narrow sothat crop is shed to either side and not pushed forwardly as the blademoves forwardly.

The side edges 23N and 23P are inclined outwardly and away from the apexat an angle A1 relative to the center line 23H of the order of 35degrees and certainly less than 45 degrees to the center line 23H.

The characteristics of the blade defined above where it is much narrowerthan conventional and significantly longer places limitations on theshape and arrangement of the beveled and serrated edges 23F, 23G.

Thus the beveled edges 23F, 23G are reduced in width at 23Q as theyapproach the front edge pointed portion 23K at the apex 23X leaving astrip 23R of the upper surface between the beveled edges with parallelside edges of the strip 23R. Thus at this strip 23R the beveled edge23F, 23G becomes narrower and the grooves 23L, 23M in the edge getshorter as the beveled edge approaches the front pointed portion 23X ofthe blade. The beveled edges 23F, 23G and the grooves 23L, 23M thereinterminate at a position spaced from the front apex 23K to define thearrow head shaped portion 23X in front of the beveled edges whichimparts sufficient strength to the construction to allow the formationof the serrations.

The cutting efficiency and therefore stubble length are also affected bythe width of the cutting edge 15B, 15C of the ledger surface 15A of theknife guard 15. Generally, the width W1 between the edges 15B and 15C atthe rear of the cutting edge on the guard in the arrangement of thepresent invention is substantially increased from the conventional widthof the order of 1.0 inches. Thus the width W1 of each guard at aposition thereon aligned with the rear end of the cutting edge of eachblade is greater than 1.0 inches. The maximum width with a blade of 2.0inches in width is slightly less than that of the width of the blade orroughly 1.9 inches. Thus with a blade of this width, the width of theguards can be as much as 1.9 inches and preferably lies in the range 1.2to 1.9 inches. However where the blade is greater than 2.0 inches inwidth, the guard has a width which is between 0.5 and 0.1 inches lessthan the width of the blade. The bottom guard also tapers so that itsedges 15B and 15C lie closely adjacent the edges of the blade when theblade and guard are in the aligned position at the end of a stroke. Thusthe angle of convergence of the edges 15A and 15B matches closely theangle A. This leaves a space S at the rear of the guards 15 at the trashbar 28 to avoid pinching crop at this location. This space S generallyshould be greater than 0.4 inches and typically is of the order of 0.5inches.

Thus the cutting system is carried so that it moves across the groundeither closely in contact with the ground as shown or at a set cuttingheight. In both cases this determines a cutting height or nominalcutting distance from the ground with is the length of any crop stalk ifcut efficiently and directly as it reaches the location between theblade and ledger surface. In FIG. 2, the cutter bar rests on the groundat a skid plate 80 which holds the ledger surface 15A at the height NDfrom the ground. Typically this is of the order of 1.5 inches but thiscan be varied slightly by changing the angle of the cutter bar about atransverse axis by changing the angle of the header.

Turning now to FIGS. 7 and 8, the shape of the pointed guard for use inthe present invention in conjunction with the pointed blade is shown anddescribed in more detail as follows.

The knife guard 30 for use in a sickle cutting apparatus 10 includes theframe structure 11, guard bar 13, sickle bar 24 and knife blades 23 aspreviously described. Each the knife blades 23 has a cutting surface 23Dfor passing across the ledger surface 15A of the knife guards 151. Eachof the knife blades has on first and second sides first and second sidecutting edges as previously described to cooperate with shearing edges152 of the guard guards 151.

The knife guard 151 includes a base portion 154 for mounting on thecutter bar 13, a rear trash bar 28 in front of the base portion 154 andat least one guard finger 153. In this embodiment three fingers 153 arearranged in a row, where the finger or fingers 153 are mounted on thebase portion 154 so that the fingers are arranged in a row along thecutter bar with a space 155 between each finger and the next allowingcrop to enter the space up to a position of engagement with the reartrash bar 28.

The guard fingers have the upwardly facing ledger surface 15A withopposed side edges arranged to provide first and second shearing edges.The guard fingers have a downwardly facing ground engaging surface 156shaped and arranged to provide protection for stone engagement as thefingers slide over the ground. That is each finger has sufficientstrength to avoid breakage when impacting stones and obstacles causingthe cutter bar to rise if the impact is sufficient and extends oversufficient number of guard fingers to provide the lifting action. Thisshape of the ground engaging surface is well known to persons skilled inthe art and includes a longitudinal rib which is generally triangular incross-section on the underside of the upper part containing the ledgersurface. The base of the rib thus forms an apex which runs over theground to prevent upward forces from snapping the guard finger at theledger surface.

An upstanding transverse shoulder 157 is provided at a front edge of theledger surface 15A and extends upwardly to a top surface 158 of thefinger where the shoulder terminates. Thus there is no tang ofconventional shape, that is no portion of the guard extending rearwardlyover the ledger surface 15A from the shoulder 158. Above the ledgesurface therefore the knife blades are free from confinement by aconventional tang as used in a conventional pointed guard or by acooperating upper guard finger of the type used in a stub guard asdescribed above.

A tip portion 159 in front of the ledger surface extends forwardly fromthe shoulder 158 and defines a forwardmost generally pointed tip 160 forengaging crop in front of the ledger surface 15A.

A length L1 of the ledger surface 15A from the trash bar 28 to theshoulder 157 is greater than 2.0 inches or more preferably greater than2.5 inches; and a length L2 of the tip portion 159 from the shoulder tothe tip is less than 1.0 inch or more preferably less than or equal to0.75 inches.

As defined previously, a center line spacing between each knife guardfinger and the next is less than 3.0 inches and preferably of the orderof 2.0 inches.

As defined previously, a width of each guard finger at the rear trashbar is greater than 1.0 inches and more preferably is greater than 1.5inches or equal to the maximum width which can be obtained while leavinga space at the trash bar between the ledger surfaces in the range 0.25to 0.5 inch or the distance necessary to avoid pinching of crop stalksbetween the ledger surfaces.

The side edges of the ledger surface 15A converge from the trash bar 28to the shoulder 15 at an angle A4 greater than 10 degrees and preferablyof the order of 12 degrees to a line LR at right angles to the trash baror parallel to the center line CL. The angle A5 of the side edges at theshoulder increases so that the tip portion is shorter than would be thecase if the angle A4 were continued up to the tip. However overall, itwill be appreciated that a line joining the rear end 161 of the sideedge 151 of the ledger surface 15A and the tip 160 converges at an anglegreater than the 10 degrees of the side edge to a line at right anglesto the trash bar.

As the side edges converge at a relatively rapid angle from the base tothe tip, the ledger surface has a width W3 at the shoulder 157 of lessthan 0.75 inches and preferably of the order of 0.5 inches.

There is also provided a plurality of separate hold down members 162arranged to engage the blades at every third spaced ones of the fingers.This has a base portion 163 mounted on the cutter bar 13 and a fingerportion 164 extending over the ledger surface of one of the fingers 14A.

1. A knife guard for use in a sickle cutting apparatus, the apparatuscomprising: a frame structure arranged for forward travel over groundhaving a standing crop thereon; a cutter bar secured to the framestructure and extending transversely across a front end of said framestructure for receiving a plurality of stationary knife guards mountedalong the cutter bar and projecting forwardly therefrom; a sickle barmounted in transversely extending position and being driven forreciprocating movement relative to said guard fingers; the sickle barhaving a plurality of knife blades mounted thereon for movementtherewith; each of the knife blades having a cutting surface for passingacross the knife guards; each of the knife blades having on first andsecond sides first and second side cutting edges to cooperate withshearing edges of said guard guards; the knife guard comprising: a baseportion for mounting on the cutter bar; at least one guard fingermounted on the base portion so that the fingers are arranged in a rowalong the cutter bar with a space between each finger and the nextallowing crop to enter the space; the guard finger having an upwardlyfacing ledger surface with opposed side edges thereof arranged toprovide first and second shearing edges; a center line spacing betweeneach guard finger and the next being less than 3.0 inches; wherein awidth of each guard at a rearmost cutting portion of ledger surface isgreater than 1.5 inches.
 2. The knife guard according to claim 1 whereina width of each guard at the rearmost cutting portion of ledger surfaceis greater than 1.75 inches.
 3. The knife guard according to claim 1wherein a width of each guard at the rearmost cutting portion of ledgersurface is equal to the maximum width which can be obtained whileleaving a space at the rearmost cutting portion of ledger surfacebetween the ledger surfaces of the order of 0.5 inch.
 4. The knife guardaccording to claim 1 wherein a width of each guard at the rearmostcutting portion of ledger surface is equal to the maximum width whichcan be obtained while leaving a space at the rearmost cutting portion ofledger surface between the ledger surfaces which is of a width distancenecessary to avoid pinching of crop stalks between the ledger surfaces.5. The knife guard according to claim 1 wherein the center line spacingbetween each guard finger and the next is substantially equal to 2.5inches.
 6. The knife guard according to claim 1 wherein the center linespacing between each guard finger and the next is substantially equal to2.0 inches.
 7. The knife guard according to claim 1 wherein a strokelength of the reciprocating movement is equal to the center line spacingbetween the guard fingers.
 8. The knife guard according to claim 1wherein the guard finger has a downwardly facing ground engaging surfaceshaped and arranged to provide protection for stone engagement.
 9. Asickle cutting apparatus comprising: a frame structure arranged forforward travel over ground having a standing crop thereon; a cutter barsecured to the frame structure and extending transversely across a frontend of said frame structure for receiving a plurality of stationaryknife guards mounted along the cutter bar and projecting forwardlytherefrom; a sickle bar mounted in transversely extending position andbeing driven for reciprocating movement relative to said guard fingers;the sickle bar having a plurality of knife blades mounted thereon formovement therewith; each of the knife blades having a cutting surfacefor passing across the knife guards; each of the knife blades having onfirst and second sides first and second side cutting edges to cooperatewith shearing edges of said guard guards; and a plurality of knifeguards according to claim
 1. 10. The sickle cutting apparatus accordingto claim 9 wherein at the position in a stroke of the reciprocatingmovement where the center line of the knife blades is aligned with thecenter line of the guard fingers, the side cutting edges of the knifeblades substantially directly overlie the side edges of the ledgersurface.
 11. The sickle cutting apparatus according to claim 9 whereineach knife blade has a front point portion in front of the side cuttingedges which front point portion has side edges converging to front apex,where the apex and the side edges of the front point portion are shapedand arranged such that crop material engaging the front point portion,as the point portion is moved forwardly in the crop, is shed to one orother side of the front point portion for cutting by the side cuttingedges and is not pushed forwardly by the front point portion.
 12. Thesickle cutting apparatus according to any claim 11 wherein the frontpoint portion has side edges which are not sharpened.
 13. The sicklecutting apparatus according to claim 9 wherein there is provided aplurality of separate hold down members arranged to engage the blades atthe fingers.
 14. The sickle cutting apparatus according to claim 9wherein each knife guard comprises a stub guard with a lower memberdefining the finger and an upper member overlying the finger with theknife blade having a length so as to project forwardly from a front tipof the upper and lower members.